Method of making patterns for die structures



Oct. 30, 1934. A z s 1,979,132

METHOD OF MAKING PATTERNS FOR DIE STRUCTURES Filed June 23, 1951 INVENTOR.

Paul I? Zz'nser WXZWW ATTORNEYS.

Patented Oct. 30, 1934 METHOD OF MAKING PATTERNS FOR DIE STRUCTURES Paul R. Zinser, Detroit, Mich., assignor to Woodall Industries Incorporated, Detroit, Mich, a corporation of Michigan Application June 23, 1931, Serial No. 546,370

3 Claims.

a. pattern for forming such a die.

An object is to provide such a die which will be inexpensive to manufacture and exceedingly durable in form. My improved process is particularly intended for use in the production of dies to be used in the stamping and shaping of thermoplastic material where cost is an important item.

In referring to the die being a deep draw grain- A ing die, I refer to a die of the deep draw characlI ter adapted to impart to the material acted upon a decorative deeply contoured surface; and wherever the word grain, grained, or graining is used throughout this specification or claims I intend it to refer to surface decoration and not some s 'ecifictype of decoration such as wood or leather graining.

An important object is the provision of a die structure of the deep draw character which has a an accurately portrayed grained surface and 5 which can be manufactured at a low cost, and my invention pertains particularly to the preparation of an inexpensive pattern to form a sand mold for such a die wherein a die may be cast in theusual manner.

It has heretofore been the practice to form these" dies by preparing a casting of the desired deep draw contour. A copper shell was then prepared in the fiat from a master matrix, and tinned on its back with soft solder and then ham- 3'5 mered on to the contoured surface of the casting to closely contact all the contours thereof, and finally the shell and casting were sweated together.

Such a die possessed many inherent disadvan- 40: tages and weaknesses. It was exceedingly difficult to fit the shell closely over the contoured surface and this was particularly difficult if the contours were represented by sharp slopes or angles as there was a tendency for the electro-de- 45. posited metal shell to break or crack when such bending was attempted. Furthermore, the bending of the shell over such a contoured surface frequently necessitated the forming of the shell in a plurality of sections and the fitting of these at several sections together upon the several faces of the casting to cover the entire contoured surface. This practice produced a die unsatisfactory in appearance and, in addition, because of the deterioration of the solder or other adhering material which secured the copper face to the cast base, the die had a tendency to break down in use under heat and pressure.

My invention comprises an inexpensive method of preparing a pattern whereby a sand mold may be made in which the die is cast. In the preparation of this pattern I provide a base form having the desired deep draw contour of the die. I then obtain a matrix of the desired surface of the die. This matrix is in the fiat.

A meritorious feature of my process resides in the forming of a plaster cast of the matrix surface. This cast is saturated with water to approximately its absorption capacity but below the point at which deterioration commences. A wax sheet or other plastic sheet reproduction of the matrix formed surface of the cast is formed on the plastic cast. This sheet, while in the plastic state, is then stripped from the cast and adhesively secured to the contoured surface of the base form. These various steps represent important features of my invention.

Other important characteristics and advantages will more fully appear from the following description, appended claims, and accompanying. drawing, wherein:

Fig. 1 is a perspective of a fragment of a plaster cast formed from the masted surface matrix,

Fig. 2 illustrates the step of immersion of the plaster cast,

Fig. 3 illustrates the step of forming the plastic sheet reproduction of the surface of the plaster cast,

Fig. 4 illustrates an additional step in the process of forming my improved pattern, and

Fig. 5 illustrates the final step in the formation of my improved pattern.

In the carrying out of my invention and the performing of the several steps which lead up to the final product, I utilize certain practices which are well known and established in the art and add to these other steps which are novel with me. I first prepare a master plate, or matrix, having the desired surface decoration which I intend to use. This master plate is constructed in the conventional manner and carries on its surface the desired wood graining or other surface decoration which I intend to have shown on the die that is made from the pattern here described.

From this master plate I prepare a casting in plaster or other suitable material according to well known principles. In Figure 1 such casting is indicated as 10 and in this figure a fragment of the casting is shown in perspective form. A

surface graining is indicated by the small lines and grooves 12.

This plaster cast is immersed in water as indicated in Fig. 2. It will be seen that the water does not cover the decorated surface formed from the matrix. Its immersion is short of that point. It is immersed in water for the length of time necessary so that it will absorb a substantial quantity of water, but not such an amount as will cause the cast to deteriorate so that the surface graining will be lost. Its absorption of water is to its normal capacity without deterioration of the surface decoration.

The plaster cast is then disposed at an angle and it may be supported as shown in Fig. 3 upon a standard and base 14 so that it is positioned at such an angle that molten material willfiow readily thereover.

The next step is the formation of a wax sheet reproduction of the matrix formed surface of the cast. I accomplish this by using a suitable waxcompound which is heated to the molten point and in this molten form is then poured to flow over the entire surface of the plaster cast and form a relatively thin uniform thickness sheet over the surface of the cast, which takes shape and form thereon. The wax sheet is indicated as 16. A suitable wax compound may be composed of the following ingredients wherein the numeral indicates parts measured by weight:

- Ozokerite wax; 38 beeswax; 1 Venice turpentine; 4 graphite. Other wax compounds might be satisfactorily employed. Before the wax has hardened a suitable adhesive 18 is applied to its upper surface. This may be a-suitable shellac.

While the adhesive is in the tacky condition and while the wax is still pliable and before it has completely hardened it is stripped from the plaster cast as indicated in Fig. 4.

This particular invention pertains primarily to the formation of deep draw dies wherein the surface contour is broken with relatively deep depressions or relatively high elevations. The invention is particularly adaptable for this type of die construction wherein it would be difficult to apply an electro-deposited copper shell to a base reference numeral 20 in Fig. 5.

- The contoured surface of this form is also coated with a suitable adhesive 22 such as shellac, and

the plastic wax sheet, after it has been stripped from the plaster cast, is placed with the adhesive side down upon this base form and pressed intimately into contact over the entire surface of the base form. Due to its plastic character it is relatively easy to force the wax sheet into close engagement over the entire surface of the form without destroying the grained surface which has been produced thereon by the plaster cast. The wax is then allowed to harden and due to the adhesive it is securely held to the base form. I then have a pattern which may be sent to the molder where a sand mold may be prepared therefrom in the usual fashion. Upon the preparation of the sand mold a metal die may be cast therein also after the conventional manner and this die used for deep drawing purposes.

Various modifications of my invention will appear from the specification and I do not wish to be limited except as by the appended claims.

What I claim:

1. In the formation of a pattern for a die; the step of forming, in the fiat, a porous plaster cast having a grained surface, partially immersing said cast in water with the grain surface above the surface of the water to absorb water to substan-' tially its absorption limit but not allowing said liquid to contact its grained surface, flowing wax over the grained surface of the cast while it retains its moisture content, and stripping the wax sheet therefrom while pliable.

2. In the formation of a pattern for a die, the step of forming a porous moisture absorbing cast having the desired surface configuration, moistening said cast to substantially its moisture absorption limit without allowing the moisture to contact with its surface configuration, and flowing a thin layer of wax over the surface of said cast while it retains its moisture content.

3. In the formation of a pattern for a die, the steps of providing a porous plaster cast with a minutely configurated grained surface, saturating the plaster cast with water without permitting the water to directly contact the grained surface thereof, applying a molten wax sheet to the grained surface of the plaster cast and filling the minute configurations thereof, coating the exterior surface of the molten wax sheet on the plaster cast with a layer of adhesive material, and stripping both the wax sheet and the adhesive material together from the grained surface of the plaster cast while the same are in a pliable state.

PAUL R. ZINSER.

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